E. P. CulverweU — Theory of the Ice Age. 55 



closely to this sjDecies tban to any other. The points of agreement 

 with Angelin's species are (1) the general appearance and amount 

 of inflation of the parts of the head-shield ; (2) the shape of the 

 glabella and its lobes ; (3) the tubercles and ornamentation on 

 the glabella and the cheeks ; (4) the presence of radial sulci ; 

 (5) the general characters of the pygidium. The peculiarities of 

 the Irish form, and its differences from the foregoing species, are 

 (1) the non-projection of the glabella beyond the fringe; (2) the 

 shape of the cheeks and their lack of any lateral overhang of 

 the fringe ; (3) the minute size and relations of the sulci, and the 

 pits in them; (4) the outward curvature of the spines. 



The lower surface of the fringe and the thoracic rings are not 

 figured by Angel in, but the Irish form has in them features not 

 found in other figured or described species. Under these circum- 

 stances the Irish form deserves to rank, for the present at any rate, 

 as a distinct species, and it may be called after its home, T. hibernicus. 



EXPLANATION OF PLATE III. 

 Fig. 1. Cybele tramorensis. x 3. 

 Fig. 2. Trinueleus hibernicus. ? Head-shield nearly perfect, showing general 



shape and characters. Variety with many lateral sulci. The glabella is 



worn and imperfect, x 3. 

 Fig. 3. Ditto. Head-shield showing lobes of glabella, tubercles, etc. X 3. 

 Fig. 4. Ditto, (f Impression of thorax and of lower surface of fringe of rolled- 



up specimen, x 6. 

 Fig. 5. Ditto. Impression of head-shield of rolled-up specimen Fig. 4. X 3. 

 Fig. 6. Ditto. Portion of upper surface of fringe, showing pits in median 



sulci. X 6. 

 Fig. 7. Ditto. Reticulate ornamentation of glabella and cheeks. X 18. 



II. — A Criticism of the Astronomical Theory of the Ice Age, 



AND OF Lord Kelvin's Suggestions in connection with a 



Genial Age at the Pole. 



By Edward P. Culyerwell, M.A., Fellow of Trinity College, Dublin. 



[Continued from the January Number, page 13.) 



(Part II.) 



IN the previous portion of this paper, which appeared in the 

 January Number, I examined the form in which CroU presented 

 ^he astronomical theory of the Ice Age and endeavoured to show 

 how absolutely unsound his argument is. It is, however, at least as 

 necessary to discuss the form in which Sir Robert Ball presents it ; 

 for much of the recent success of the theory, outside the school of 

 modern geologists, was due to the weight naturally attached to the 

 fact that a writer of Ball's scientific eminence believed he had so 

 materially strengthened CroU's astronomical argument, that had 

 CroU himself been aware of its full force, he would not have felt 

 bound to call in such auxiliary agencies as a diversion of the Gulf 

 Stream from its course. If, then, the theoiy, as presented by 

 CroU, was able to win its way with such success among scientific 

 authorities, it must surely be irresistible in the new and more 

 powerful form. But it will be seen that, so far from strengthening 

 CroU's position, Ball's statement weakens it very materially. 



